Got a 744H that suddenly lost main hydraulic power to boom and bucket, will still steer and drive. Only makes 100-200psi out of all the test ports I found. You can see the rams move slightly when controls are actuated but nothing more. No metal in filters. Anybody see this before with some tips of where to start.
Machine serial number? Has the F16 Pilot Enable Fuse been checked?
Sn- DW744HX583295 Fuses are good
Has the pilot pressure been checked?
Which port is the pilot pressure? Pretty sure I hooked up to them all. Around 100-200psi. Most I got was off the steering pump when engaging steering.
So when I hook it up to the test port on top of main pump it's at 0 bar, I actuate boom up it slowly climbs up to 3 bar, at full throttle 7 bar, if I actuate steering it spikes to 25 bar.
Test port at bottom of main pump reads 6 bar no matter what is actuated, Test ports at gold block labeled "reg press" and "pump press" both read 12bar and go up to 15 at full throttle, spike to 30 with steering input.
That hydraulic system is too hard to explain here. Essentially, the diagnostic coupler on the top of the pump is the load sense. It will not read anything until a function is actuated. The diagnostic coupler at the pump output line is obviously pump output pressure and that should be at least 48 bar with no functions activated. "REG PRESS" at the block on the side of the frame should always be 41+ bar with no functions activated. I'll put some information together for you. Check your messages. Might be a day or two.
I definitely have an issue since I have nowhere near that pressure. I appreciate all the help!
Ok, did the pressure reducing valve pressure test, was low so I adjusted to 44 bar. On to next test. Isolated pumps by capping priority valve discharge hose. Connected gauges to pump output and load sense, I get zero. No pressure at all no matter what.
Sounds like a pump drive or a pump failure.
Had a feeling it was gonna be that. Thank you for all the info. What is the best method to remove? Can I get it out without removing cab?
I have done smaller wheel loaders without removing the cab. It takes some creativity to get the pump out due to the weight. I couldn't tell you if it can be done on the 744. Knowing how heavy that pump is, I myself would be pulling the cab.
I got it out through the side. Pump shaft and coupler destroyed themselves. Allen holding coupler in snapped off but coupler still wont come out. Can that assembly come out as one?
I don't remember, to be honest. I believe the the pump drive shaft can be removed without transmission disassembly. I think the pump mounting flange and the transmission pump need to be removed to do that.
Would you happen to have a breakdown of that transmission?
Check your messages. Besides what I sent, the parts book would be the next best thing.
Thank you!
Got it all out. Here's the damage.